Laminated veneer lumber (LVL) is a densified wood product composed of multiple strips or sheets of wood veneer that are laminated together using heat, pressure and exterior quality adhesive, to form thick panels. The wood-grain in the sheets of veneer is normally in the same longitudinal direction in order to maximize the available strength and stiffness of the resultant LVL material. This alignment of the wood fiber, together with the dispersion of wood defects such as knots, enables LVL products to be used at higher structural design loadings than conventional solid wood.
LVL is widely used in the form of structural beams, headers, columns and posts in both residential and commercial applications. LVL is also used in miscellaneous applications such as truck beds and concrete forms.
LVL is made from veneers obtained from logs of broad-leaved trees such as lauans and beech wood, or of acicular trees such as North American woods, Japanese cypress and cedar by chopping the log into cross segments of a given length and cutting the segments into veneer sheets of 2-3 mm thickness using a rotary lathe. The veneer sheets are then dried, laminated by arranging them in parallel in the grain direction and bonded with an adhesive.
The structural properties of the resultant LVL is predominantly determined by the quality of the wood veneer sheets that are used. The quality of the wood veneer sheets can vary considerably depending upon the source of the original lumber. High grade timber is becoming increasingly scarce and in general, wood quality is declining as more juvenile and second growth wood is being harvested for veneer production. Therefore, it is becoming more important to be able to enhance the structural properties of LVL panels that are made from lower grade veneer sheets.
Under certain loading conditions, LVL panels may have insufficient structural properties in the direction that is perpendicular to the grain direction. For example, conventional LVL panels sometimes exhibit a cupping problem where the whole panel becomes slightly curved. Such problems may become worse if lower grade veneers are used in the manufacture of the LVL. It is also commercially attractive for a manufacturer if it can use lower quality, less expensive veneers and yet still achieve an acceptable level of structural performance from the LVL material so produced.
The engineered fabric reinforced LVL panel of the present invention provides superior structural properties compared to unreinforced conventional LVL. The LVL panel of the present invention has at least one sheet of an engineered fabric that is disposed between conventional veneer sheets to reinforce the LVL panel.
The reinforced LVL panel of the present invention provides excellent load bearing characteristics even when lower quality veneer sheets are used partly due to the novel employment of reinforcements.